Britain’s Super Spiders

Ero aphana. One of the sneakiest and most specialised spider assassins (c) Tone Killick

Ero aphana. One of the sneakiest and most specialised spider assassins (c) Tone Killick

October is perhaps the only month of the year when it’s socially acceptable to decorate your house with spiders as we revel in all things ‘spooky’. So it’s only natural that arachnid enthusiasts have adopted  it as a month-long celebration of all things spider, dubbed Arachtober, aiming to share the wonder of these arachnids and turn fear into fascination.

Having been around for over 380million years (before our own ancestors even stepped out on land), spiders are some of the planet’s most accomplished predators, consuming millions of tonnes of insects and having positive effects on the ecosystem . They really do deserve more credit, especially in the UK where none of them are dangerous despite what the media says. Spiders are fantastically diverse (with 650 species in the UK alone) and have evolved many incredible strategies to catch their prey. Let’s delve into the hunting strategies of eight of the Britain’s most awesome arachnids.

Flower crab spider – Hiding in plain sight

Spot the spider- a Flower crab spider waits on a buttercup.

Spot the spider- a Flower crab spider waits on a buttercup.

Insects love flowers, and Flower crab spiders (Misumena vatia) have evolved to exploit this. Waiting on the blooms with long, outstretched forelimbs ready to grab a passing pollinator, these spiders can change from white to yellow to match their colourful perch. They even mimic a flower in the UV spectrum, which many pollinating insects (like bees and butterflies) see in. This not only masks the crab spider’s identity, it makes them more attractive than the flower they’re sitting on, meaning insects make a bee-line the spiders deathly hug and fast-acting venomous bite.

 

Pirate spider – Stealth mode

A Pirate spider feeds on its spider prey (c) John Brookes

A Pirate spider feeds on its spider prey (c) John Brooks

Flower crab spiders may want to attract their prey, but the success of Pirate spiders Ero spp. relies mainly on going undetected. Their chosen prey is other spiders-specifically comb-foot spiders (family theridiidae), which make webs. Hunting a spider on its own web is a precarious business, as any vibration on the strands could alert the comb-foot and result in the pirate becoming lunch instead!  So the pirate spider plays the long game, gradually creeping imperceptibly closer to the comb-foot, sometimes taking hours to reach the spider. When eventually it is close enough, the pirate arches it’s long ,spiny forelimbs and in a sudden burst snatches the spider and bites it on the leg, paralysing and killing it near-instantly.
Cellar spider -Fragile yet fierce

A Cellar spider feeds on a much beefier House spider (c) Paul Mingo.

A Cellar spider feeds on a much beefier House spider (c) Paul Mingo.

Often found suspended from wispy criss-cross webs in houses, Pholcus phalangoides is also known as the Daddy longlegs spider (creating some confusion with craneflies) after it’s long, delicate legs-prone to breaking if grabbed.  Yet these fragile waifs are killers of the biggest and burliest house spiders.

Once falsely thought to have potent venom (the origin of the venomous daddy longlegs myth), it’s actually their lengthy legs which are key to their success. When another spider or insect stumbles in their web, they fling silk with their legs to wrap it, keeping their bodies well out of range of retaliating jaws or fangs. Eventually the prey is tightly swaddled with silk and immobilised, allowing the meeker predator to deliver killing bites with nips to the leg
joints. The appearance and habits of this species have led some to dub it
the ‘slenderman of spiders’.

 

Spitting spider – Lethal ejection

A Spitting spider with a planthopper it has immobilised (c) Fritz Geller-Grimm.

A Spitting spider with a planthopper it has immobilised (c) Fritz Geller-Grimm.

The spitting spider Scytodes thoracica avoids the danger of touching its prey entirely. This nocturnal stalker of indoor walls and ceilings can be identified by it’s leopard-print markings and it’s bulbous head housing special silk glands. When this spider encounters prey, it fires rapid double stream of sticky silk in a zigzag pattern from its head, pinning down the victim like a gladiator’s net. It’s a little like the silly string deployed by disgruntled trick or treaters, but with added punch. To make doubly sure the prey can’t escape, the silk is laced with venom from the spitter’s venom glands. All the spitting spider has to do is walk up to the incapacitated victim and feed at its leisure.

 

Woodlouse spider – Tools of the trade

A male woodlouse spider-check out those chelicerae (c) Hans Hillewaert

A male woodlouse spider-check out those chelicerae (c) Hans Hillewaert

With their cream abdomen, neon orange legs, deep red cephalothorax (front section) and huge, projecting fangs, Woodlouse spiders Dysdera spp. are often mistaken for something exotic and could make this list by appearance alone. These spiders have evolved their impressive weaponry to deal with armoured prey- woodlice.  They are the woodlouse’s neighbours from hell, dwelling in the same dark, damp habitats and seeking prey by touch. Although their fangs easily pierce through a woodlouse’s carapace, the woodlouse spider doesn’t simply bite into it with brute force. Using it’s huge jaws like a claw arm, the spider lifts the woodlouse, rotates it and inject its soft underbelly with venom.
In case you’re wondering, these fangs can give a painful (though harmless) defensive bite, although it’s no wonder that these blind, soft-bodied spiders feel the need to stick up for themselves if prodded by our giant digits.

 

Purse-web spider- Slash and grab

A male purse-web spider. Generally only males wander from their underground webs in search of mates. Check out THOSE chelicerae! (c) Siga

A male purse-web spider. Generally only males wander from their underground webs in search of mates. Check out THOSE chelicerae! (c) Siga

The Purse web spider Atypus affinis is Britain’s only member of the early Mygalomorph group of spiders- which also includes the trap door spiders and tarantulas of warmer climes. A defining feature of this group is their downward-pointing fangs, and Atypus has a huge pair of these that put a woodlouse spider to shame! The namesake purse-web of this spider is more like a subterranean silk sock woven into a burrow and closed off at both ends, with the sole exposed at the surface. The spider completes her trap by camouflaging it with soil. When an insect stumbles across the silk, she rushes over to position herself underneath it, then violently stabs through the web with her fangs to grab and inject the prey. However,  to eat it she must get it inside. The inside edge of her mouthparts (or chelicerae) have a serrated edge like a saw to help her scissor through the silk, cutting a slit to drag the prey through, which she dutifully webs up again before feeding.

 

 

Raft spider- Fishing for supper

A Fen raft spider floats on the water surface (c) Steven Falk.

A Fen raft spider floats on the water surface (c) Steven Falk.

Spiders have even made moves into the water. The Raft spiders Dolomedes spp. are amongst our largest spiders. They spend much of their time on the shores of freshwater pools ,where despite their weight, they’re supported on the surface tension thanks to water-repelling hairs . Here they sit with their forelegs touching the surface, waiting for vibrations caused by a drowning insect or aquatic creature. The spiders run out across the water to grab their prey and can even dive in. While most of their food is invertebrates, their size, strength and venom allows them to eat small fish and amphibians too.  Raft spiders respond to the bigger vibrations of a predator by diving underwater-where they can remain hidden for several minutes thanks to hairs retaining air bubbles around their lungs.

Unfortunately, both our species of raft spider are now rare due to the loss of their wetland habitats, but the Fen raft spider D.plantarius is being helped through dedicated conservation efforts. Learn more here.

Watch a raft spider go fishing:

 

Water spider- The life aquatic

A pair of water spiders (male on right). The silvery appearance comes from the air bubble trapped against the spider's abdomens.

A pair of water spiders (male on right). The silvery appearance comes from the air bubble trapped against the spider’s abdomens (c) Baupi.

The Raft spider may be able to visit the underwater realm, but the Water spider Argyronteta aquatica is the only species able to spend its life there. How it does so is alluded to in its other name, the Diving bell spider.

Water spiders have a thickly-haired abdomen which helps them to retain air from the surface much like the raft spider, but far more efficiently. Each time the water spider surfaces it creates its own silvery scuba tank, allowing it to paddle around and crawl along waterweeds. The spider builds a small sheet web among aquatic plants, then releases some of the air bubble underneath it. After repeat visits, the web stretches into a bell shape which forms the spider’s home. Thanks to the structure of the water spider’s silk, it doesn’t even have to refresh the supply as oxygen diffuses into the bell from the surrounding water. From here, the spider builds criss-cross lines to intercept a menu of  aquatic insects, shrimps, tadpoles and small fish. It must drag these back into it’s air bell to feed, since like all spiders Agryroneta break down their meals
with digestive juices which would get diluted in water.

Watch a water spider create an air bubble in which to feed on the shrimp it’s killed.

Want to find out more about these amazing arachnids?

Need help identifying a UK spider? Post it on the UK Spiders or the British Spider Identification Group facebook pages for expert help.

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RoryD

RoryD

Conservation Ecology graduate with a particular interest in entomology. Pleased to be a volunteer and subcontractor with Buglife. Views and fixations are my own.
RoryD

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